College focuses

Hello all!
I was wondering a lot about colleges and their focuses on gpa and I’ve been told different things. A lot of people have told me that colleges look more for improvement over time while others tell me they look for it from the get go.

In addition, as long as I meet the overall cumulative GPA requirement for any given school is that all that matters? Basically, are colleges going to go into detail about what grades I got in every class for all 3 years of high school, or are they going to look at that number and be satisfied regardless of my individual grades?

One last thing; how much does your chance of getting into a college increase if you have siblings attending there? Especially for the ivy leagues. I know it can’t be by much but it would still be nice to know how much it affects your application if your sibling has accomplished great things. Obviously that doesn’t mean you would do the same but just how much thought do they put into that ?